As I’m sure most people have seen before in the closest streaming service documentary, whales are truly beautiful creatures. Being graceful swimmers whose sheer size have been the stuff of literal legends, these animals—collectively known as cetaceans, which include whales, dolphins, porpoises, and orcas, among others—took advantage of their environment through eons of evolutionary time to achieve their truly colossal sizes. Yet, of course, they weren’t always this way. Much like the rest of the mammals on Earth, whales too had ancestors that walked on land.
The cetaceans themselves evolved from the artiodactyls, or the even-toed ungulates. These animals encompass a vast swath of animals, such as deer, giraffes, pigs, camels, and what would be the ancestors of whales. The earliest known definitive whale ancestor was a 50-million-year-old quadruped called Pakicetus, which looked like an odd wolf. It hunted near bodies of water in what is now Pakistan, hence the name of the genus. These animals, at first glance, seem to bear no immediate resemblance to the giants of the seas that we know today.
Being mammals, whales too have domes of bone that cover their middle ear, called tympanic bullae. Whales, however, have tympanic bullae that have very thick and dense inner edges—so thick that they garnered their own name in whales: the involucrum. And, much like all cetaceans alive today, Pakicetus had an involucrum too, making it the earliest known whale ancestor. This meant that, according to current understanding, cetaceans originated from the Indo-Pakistani oceanic region, then dispersed across the world through the seas—letting go of hundreds of millions of years of evolution that took place after their distant tetrapod ancestors first walked on land.
From here, cetaceans diversified into new forms, with each new species gaining newer and better adaptations to move from being ostensibly mammalian crocodiles to truly aquatic creatures. New findings published in the journal Proceedings of the Royal Society B: Biological Sciences will add yet another member to the growing whale family tree, giving more detail to its long story: a 3-m (10-ft) long beast called Phiomicetus anubis.
P. anubis lived some 43 million years ago, in what is now Egypt. Estimated to weigh about 600 kg (1,300 lbs), the animal’s skeleton seemed to be a cross between a wolf and a crocodile; it probably hunted crocodiles in its area too, given its skull features that may have anchored powerful jaw muscles. What granted the animal its name, however, is two things: the Fayum Depression—the place where it was found—and the shape of its skull: it bears resemblance to Anubis, the Egyptian god of death with the head of a jackal. P. anubis belonged to the Protocetidae, a group of whales that were in the middle of the transition from terrestrial to fully-aquatic mammals. This also makes P. anubis the earliest-known protocetid whale discovered in Africa.
The “Anubis” whale was found in the Fayum Depression, inside Egypt’s Western Desert, back in 2008. The expedition that led to its discovery was spearheaded by study co-author Mohamed Sameh Antar, who was also a vertebrate paleontologist for the Egyptian Environmental Affairs Agency . During the time when P. anubis was still alive, this area of Egypt was a seabed; in fact, this area had already yielded other whale ancestors before, like Rayanistes afer. It appears that the two actually coexisted in the same area at around the same time, yet probably occupied two separate ecological niches. It’s possible, then, that P. anubis hunted the young of other ancient whale relatives like R. afer. The two lived alongside other sea creatures of the Eocene epoch, like sea cows.
Abdullah Gohar, lead author of the study and researcher from the Mansoura University Vertebrate Paleontology (MUVP) Center, described the animal as a “key new whale species” and a “critical discovery for Egyptian and African paleontology.” The newly-discovered whale also raises questions about where it once lived, and how it sustained these various creatures, according to co-author and MUVP founder Hesham Sellam.
Bibliography
- Black, R. (2010, December 1). How Did Whales Evolve? Smithsonian Magazine. Retrieved September 9, 2021, from https://www.smithsonianmag.com/science-nature/how-did-whales-evolve-73276956/
- Black, R. (2015, January 5). Science Word of the Day: Involucrum. National Geographic. Retrieved September 9, 2021, from https://www.nationalgeographic.com/science/article/science-word-of-the-day-involucrum
- Geggel, L. (2021, August 26). Walking whale ancestor named after Egyptian god of death. LiveScience. Retrieved September 9, 2021, from https://www.livescience.com/ancient-whale-god-of-death.html
- Morad, M. (2021, August 26). Fossil of previously unknown four-legged whale found in Egypt. Reuters. Retrieved September 9, 2021, from https://www.reuters.com/lifestyle/science/fossil-previously-unknown-four-legged-whale-found-egypt-2021-08-25/
- Gohar, A. S., Antar, M. S., Boessenecker, R. W., Sabry, D. A., El-Sayed, S., Seiffert, E. R., Zalmout, I. S., & Sallam, H. M. (2021). A new protocetid whale offers clues to biogeography and feeding ecology in early cetacean evolution. Proceedings of the Royal Society B: Biological Sciences, 288(1957), 20211368. https://doi.org/10.1098/rspb.2021.1368
